The present invention relates to a device for providing a static and a dynamic seal between a rotatable shaft and a housing. In particular, the present invention relates to a seal cartridge which includes a labyrinth portion and a contact portion, while providing protection to the rotating shaft from contact by the contact portion.
Prior art devices for sealing a rotating shaft are disclosed in U.S. Pat. No. 4,022,479 (Orlowski). Seal devices of this type may be used to inhibit oil from escaping out of a bearing housing and/or to inhibit contaminants from working their way into the housing. The prior art devices are formed of at least two ring-shaped members that rotate with respect to each other when the shaft is rotated. One of the members is fixed to the housing and does not rotate. The other member rotates with the rotating shaft.
The two ring members should be located very close together, particularly when the seal device is used to isolate the bearing from small particulate contaminants. Even small quantities of such contaminants are capable of significantly deteriorating the bearing. To prevent such contamination, the two relatively rotatable ring members must be held together very closely, with only a very narrow space therebetween.
The ring members of the Orlowski seal device are connected together by a separate securing means, not shown in the prior art patent. The ring members themselves have no means for establishing and maintaining a narrow spacing therebetween. Therefore, the prior art seal device cannot be manufactured as a unit with a preset, fixed spacing. The spacing between the ring members has to be set when the seal device is installed into the housing. This leaves room for human error outside the control of the device manufacturer. In particular, the Orlowski device can be improperly installed, with the ring members located too far apart to perform satisfactorily. Another problem with the Orlowski device is that the ring members may be separated subsequent to installation, for example by high pressure cleaning spray.
Prior art devices showing labyrinth and/or contact seals are disclosed in U.S. Pat. Nos. 5,259,628 (Nisley), 5,028,054 (Peach), and 4,379,600 (Muller). The device referred to in Muller is a dust seal between an inner race and an outer race. The dust seal is accomplished either through a labyrinth arrangement of L-shaped rings or through a contact seal. The device of Muller provides no mechanism for sealing, either dynamically or statically, fluid from exiting the device.
The device disclosed by Nisley is a seal assembly with a rotor, a housing, a V-ring and a metal ring. The housing and the rotor have alternating teeth and grooves which intermesh to form a labyrinth seal. The metal ring fits within an angular groove in the housing. The V-ring is positioned on the rotor and makes contact with the metal ring on the air side of the device. The device as disclosed by Nisley is, thus, formed of four separate machined pieces, and is relatively expensive to manufacture. Such a seal device, since it has four separate parts which must be fit together, will have correspondingly greater leakage points than a seal device with fewer parts. Further, the V-ring is positioned to make contact with a metal ring, which may wear the V-ring, leading to an opening between the housing and the rotor through which contaminants and fluid may travel.
The device referred to in Peach has, like Nisley, numerous separately machined or formed parts, thus increasing the device""s complexity and possibility of leakage.
U.S. Pat. No. 5,522,601 (Murphy) refers to a locking labyrinth sealing assembly where a flange on a rotor wraps around and interlocks with a flange on a stator. The Murphy device, however, fails to disclose or suggest a contact portion on the oil side and a wholly non-contact portion of the seal on the air side, nor does it show the stator contacting the rotor on the oil side. Furthermore, the Murphy device does not include a cartridge device acting as a rotor.
U.S. Pat. Nos. 4,981,303 (Matsushima et al.) and 4,596,394 (Schmitt) refer to sealing devices having contact portions on both the oil side and the air side.
The disadvantages of the prior art are alleviated to a great extent by the present invention which provides a seal cartridge including an interlocked two-piece non-contact labyrinth seal portion, with a rotor and stator, as well as a contact lip seal portion.
In a preferred embodiment, the invention provides a two-piece, interlocked seal device adapted to be mounted upon a rotatable shaft. The seal device includes a rotor with a flange, a radially outwardly directed groove, and a radially outwardly directed surface, and a stator with a cover having an annular notch and a radial opening adapted to direct contaminants from the seal, a radially inwardly directed ridge, and at least one flange biased toward the rotor surface. The stator ridge is positioned within the rotor groove and the rotor flange is positioned within the stator annular notch to create a labyrinth portion and the stator flange and the rotor surface create a contact portion.
In one aspect of the invention, the two-piece, interlocked seal device includes a stator having a cover with an annular notch and a radial opening adapted to direct contaminants from the seal, a radially inwardly directed ridge including an inclined surface, and a plurality of flanges biased toward the rotor surface.
The invention further provides a sealed system including a housing, a rotatable shaft and a two-piece seal device. The seal device includes a rotor having a flange, a radially outwardly directed groove, and a radially outwardly directed surface, and a stator having a cover with an annular notch and a radial opening adapted to direct contaminants from the seal, a radially inwardly directed ridge, and at least one flange biased toward the rotor surface. The stator ridge is positioned within the rotor groove and the rotor flange is positioned within the stator annular notch to create a labyrinth portion and the stator flange and the rotor surface create a contact portion.
An object of the invention is to provide an interlocked two-piece seal having a labyrinth seal portion and a separate, contact portion for both static and dynamic sealing. Forming the seal of only two pieces is advantageous. A two-piece seal may have fewer leakage paths than a seal having a greater number of pieces. Moreover, a two-piece seal may be more economical to manufacture and more reliable.
Another object of the invention is to provide a contact portion which provides a static seal during flooded conditions.
Another object of the invention is to provide a seal device that can be easily installed on a shaft without the need to repair or specially finish a worn or damaged shaft.